text: It is essential that the microcapsules have adequate membrane strength (mechanical stability) to endure physical and osmotic stress such as during the exchange of nutrients and waste products. The microcapsules should be strong enough and should not rupture on implantation as this could lead to an immune rejection of the encapsulated cells. For instance, in the case of xenotransplantation, a tighter more stable membrane would be required in comparison to allotransplantation. Also, while investigating the potential of using APA microcapsules loaded with bile salt hydrolase (BSH) overproducing active Lactobacillus plantarum 80 cells, in a simulated gastro intestinal tract model for oral delivery applications, the mechanical integrity and shape of the microcapsules was evaluated. It was shown that APA microcapsules could potentially be used in the oral delivery of live bacterial cells. However, further research proved that the GCAC microcapsules possess a higher mechanical stability as compared to APA microcapsules for oral delivery applications. Martoni et al. were experimenting with bacteria-filled capsules that would be taken by mouth to reduce serum cholesterol. 
  The capsules were pumped through a series of vessels simulating the human GI tract to determine how well the capsules would survive in the body. Extensive research into the mechanical properties of the biomaterial to be used for cell microencapsulation is necessary to determine the durability of the microcapsules during production and especially for in vivo applications where a sustained release of the therapeutic product over long durations is required.
  van der Wijngaart et al. grafted a solid, but permeable, shell around the cells to provide increased mechanical strength.
  Sodium Citrate is used for degradation of alginate beads after encapsulation of cells. In order to determine viability of the cells or for further experimentation. Concentrations of approximately 25mM are used to dissolve the alginate spheres and the solution is spun down using a centrifuge so the sodium citrate can be removed and the cells can be collected.